1. Field of the Invention
The present invention relates to a vehicle with a cabin, in which the cabin is supported by a vehicle body.
2. Description of the Related Art
As disclosed in JP 2002-356184, for example, a vehicle with a cabin is known as a conventional technique in which an acoustic absorbent sheet is provided to the floor, the ceiling wall, and other parts of the steering unit of the cabin so as to reduce noise inside the cabin.
In the vehicle with a cabin disclosed in the above reference, a configuration is adopted in which the in-cabin noise is transmitted to an acoustic absorbent material via a plurality of holes formed in the surface of the acoustic absorbent sheet, and noise inside the cabin is reduced through the sound-absorbing effects of the acoustic absorbent material. However, the noise inside the cabin is not reduced by reducing vibration transmitted from the vehicle body to the floor surface, ceiling walls, and other parts of the steering unit. As a result, even when the acoustic absorbent sheet is provided to the floor, ceiling walls, and other parts of the steering unit, not only are the noise-reducing effects minimal for the surface area in which the acoustic absorbent sheet is affixed or provided, but noise inside the cabin cannot be adequately reduced, and noise caused by vibration that is transmitted from the vehicle body to the floor, ceiling walls, and other parts of the steering unit contributes significantly to in-cabin noise, which continues to cause discomfort to the operator.
In the vehicle with a cabin disclosed in the abovementioned reference, a configuration is adopted in which noise inside the cabin is reduced by affixing or providing an acoustic absorbent sheet having a wide surface area over a wide range that includes the floor, ceiling walls, and other parts of the steering unit. As a result, drawbacks occur in that the cost of the acoustic absorbent sheet increases; the manufacturing cost of the vehicle markedly increases; a large amount of time is required to affix or provide the acoustic absorbent sheet to the floor, ceiling walls, and other parts of the steering unit; and the productivity of assembling the vehicle is adversely affected.
Therefore, a reinforcing member, a steel plate for suppressing vibration, or the like may be attached to the floor, ceiling walls, and other parts of the steering unit to reduce vibrations transmitted from the vehicle body to the floor, ceiling walls, and other parts of the steering unit, and to reduce the in-cabin noise that is uncomfortable to the operator. However, when a reinforcing member, a steel plate for suppressing vibration, or the like is attached to the floor, ceiling walls, and other parts of the steering unit, drawbacks occur in that the manufacturing cost of the vehicle markedly increases, and the weight of the vehicle increases in conjunction with attaching the reinforcing member, the steel plate for suppressing vibration, or the like.
As disclosed in JP 8-142776, a soundproofing structure for a vehicle is known as another conventional technique in which an acoustic absorbent material is provided between an inner lining material and a door body so that noise inside the cabin can be reduced by the door.
In the vehicle soundproofing structure according to JP 8-142776, a configuration is adopted in which the acoustic absorbent material is housed inside the inner lining material, noise that penetrates into the door body from the joint or the like between the inner lining material and the door body is transmitted to the acoustic absorbent material, and the noise inside the cabin can be reduced, but the in-cabin noise is absorbed by the inner lining material, and is less likely to be transmitted to the acoustic absorbent material. As a result, the noise that occurs inside the cabin is less likely to be absorbed by the acoustic absorbent material, and there is room for improvements to be made to reduce the noise inside the cabin.